The present invention relates to an uncrosslinked hydrogel, to its process of preparation as well as to its applications as an article for medical and/or surgical purposes such as tubes, filaments, films, joints, implants and the like, particularly in ophthalmology.
It has already been proposed, to employ polymers in hydrogel form having a relatively high water content whilst having improved mechanical and optical properties (European patent No. 188 110 and U.S. Pat. Nos. 4,379,864 and 4,543,371), for ophthalmic purposes.
However, the product described in U.S. Pat. Nos. 4,379,864 and 4,543,371 do not show a high water content; these polymers lose, in fact, the required mechanical properties, particularly for their use as an implant, when the water content is high.
As regards the hydrogel described in European patent application No. 188 110, they do not show properties of good tolerance, particularly required for an implant, to the extent that the ionic characteristics and in particular the electronegativity of the polymer does not permit good tolerance of the latter to be envisaged.
This is why Applicant has sought in another direction for a solution to the problem set, which is that of providing hydrogels having high biocompatibility for their use in the preparation of articles for medical or surgical purposes which are highly reliable and in particular ocular implants enabling a suitable permeability to be obtained to different biological molecules, said implants, not showing, consequently, the drawbacks of known implants.
Patent FR 2 529 464 described biocompatible materials in the form of hollow fibers or membranes. These biomaterials are treated by a plurality of drawings to produce a suitable permeability and showing for this reason, a different structure, namely of membranes or hollow fibers for hemodialysis and/or hemofiltration.
Patent DE-A-2028956 described a hydrogel which comprises many ionic groups, said hydrogel not showing the suitable biocompatibility sought by Applicant.
Applicant unexpectedly has found that certain biomaterials under particular condition, have considerable advantages, especially in the field of ocular implants.
It is, in this respect, an object of the invention to provide an uncrosslinked hydrogel with improved mechanical properties and with a high water content as well as its method of preparation which responds better to the necessities of practice than the hydrogels of the prior art, particularly in that they have the advantage of conferring on said hydrogels a character of inertia with respect to biological cells.
It is also an object of the invention to provide articles constituted by or comprising said hydrogel. The use of said articles in surgery and in medicine is also an object of the invention. Among said article, may be mentioned especially ocular implants which show besides the character of inertia with respect to biological cells:
the following optical properties: PA0 physico-chemical properties such as: PA0 particular biological properties such as:
perfect transparency in visible light, PA1 absorption of ultra-violet rays at 280 nm, PA1 refractive index close to that of the cornea. PA1 high permeability to water, to physiological serum, to small and medium-sized molecules, assuring the migration of nutrient substances for the cornea as well as all of the metabolites, PA1 permeability to dissolved gases (O.sub.2, CO.sub.2), highly hydrophilic PA1 a chemical nature devoid of toxic groups, of heavy metals, of remaining catalysts and of free monomers and of solvent easy to use, PA1 dimensional stability, especially in a 0.9% chloride solution PA1 be non-bioresorbable in the physiological medium, PA1 have good resistance to aging in this medium, that is to say not showing opacification, coloration or degradation of physical properties. PA1 show good tissue tolerance of the sites of implantations in the corneal stroma, without causing alteration of the epithelium and of the corneal endothelium PA1 have, if possible, a low affinity for proteins, PA1 be sterilizable and/or re-sterilizable.